Asphalt IS a bit softer.  Especially here.  You can even dimple it with your thumb if you press hard enough on a hot day (AND if you want to burn you finger)...

Also, if you don't have a block or something to stand your motorcycle on, the kickstand will punch into it and fall over.

I could swear it feels a bit softer to me, but it would be an interesting blind test if you could pull it off...

As for the cross slope, TECHNICALLY, if properly designed and constructed, the sidewalks should tilt towards the street at 2% crossslope.  The stress should ALSO slope at 2% towards the curb and gutter, so really, the cross slope should be the same and make no difference.

But who's to say how it was built or designed in you neck of the woods.

Med Sci Sports Exerc. 2009 May;41(5):1138-45.

Training surface and intensity: inflammation, hemolysis, and hepcidin expression.

Peeling P, Dawson B, Goodman C, Landers G, Wiegerinck ET, Swinkels DW, Trinder D.

PURPOSE: This investigation assessed the effects of training intensity and ground surface type on hemolysis, inflammation, and hepcidin activity during running. METHODS: Ten highly trained male endurance athletes completed a graded exercise test, two continuous 10-km runs on a grass (GRASS) and a bitumen road surface (ROAD) at 75%-80% peak VO2 running velocity, and a 10 x 1-km interval running session (INT) at 90%-95% of the peak VO2 running velocity. Venous blood and urine samples were collected before, immediately after, and at 3 and 24 h after exercise. Serum samples were analyzed for circulating levels of IL-6, free hemoglobin (Hb), haptoglobin (Hp), iron, and ferritin. Urine samples were analyzed for changes in hepcidin expression. RESULTS: After running, the IL-6 and free Hb were significantly greater, and serum Hp was significantly lower than preexercise values in all three conditions (P < 0.05). Furthermore, IL-6 levels and the change in free Hb from baseline were significantly greater in the INT compared with those in the GRASS (P < 0.05). There were no differences between the GRASS and ROAD training surfaces (P > 0.05). Serum iron and ferritin were significantly increased after exercise in all three conditions (P < 0.05) but were not different between trials. CONCLUSION: Greater running intensities incur more inflammation and hemolysis, but these variables were not affected by the surface type trained upon.

I know I'm way late in talking on this subject.  Just signed up.  Anyway, here's the skinny on asphalt vs. concrete. Concrete = 150.01 psf  Asphalt = 140 psf  That's a 7% difference.  Since we take over 30,000 foot strikes in a marathon..... It makes a difference.  http://www.aqua-calc.com/page/density-table

Scott

Well, to be precise, the study found no difference on the variables they investigated. What the results of the study mean depends on whether you believe those variables are the best indicators of the outcomes we care about. Until they find a reliable way of measuring Total Global Runner Happiness Factor, we will be stuck looking at a lot of different variables and wondering how well they represent what we care about.

Going the other way, it's perfectly possible that a measurable 7% difference in surface hardness is not enough difference to influence Total Global Runner Happiness (or its associated variables investigated in the linked study).

See, this is the cool thing about research - we're always getting new bits and pieces of data, without ever definitively answering the question.

Haha! That is so true!

For some reason, I used to think the asphalt was harder, but noticed a touch more soreness after running on the sidewalks. This would be from going back & forth on the two at different points of the runs. Then I did actually look up the values.

Something else that has come up in a study is the people will adjust their stride a bit for the surface. One result of that is how well does that study listed above still apply? Another is that how much does the surface still matter if we adjust accordingly? I think in there it will depend on ones ability to adjust.

This has come up before and it was brought up that the deflection was ridiculously small compared to the shoes and leg movement available. While true, I still wonder why static force logic was applied to a dynamic system. What happens to the energy?